Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features
The Indian Institute of Geomagnetism (IIG) in 1982, 1986, and 1996, operated a Proton Precession Magnetometer (PPM) at its Antarctic stations Dakshin Gangotri/Maitri (located at ∼70°S, ∼12°E). Comparison of the average quiet-time value of total intensity F for these years with values of F obtained a...
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crcambridgeupr:10.1017/s0954102002000585 2024-04-07T07:47:32+00:00 Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features Rajaram, Girija Arun, T. Dhar, Ajay Patil, A.G. 2002 http://dx.doi.org/10.1017/s0954102002000585 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102002000585 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Antarctic Science volume 14, issue 1, page 61-68 ISSN 0954-1020 1365-2079 Geology Ecology, Evolution, Behavior and Systematics Oceanography journal-article 2002 crcambridgeupr https://doi.org/10.1017/s0954102002000585 2024-03-08T00:36:32Z The Indian Institute of Geomagnetism (IIG) in 1982, 1986, and 1996, operated a Proton Precession Magnetometer (PPM) at its Antarctic stations Dakshin Gangotri/Maitri (located at ∼70°S, ∼12°E). Comparison of the average quiet-time value of total intensity F for these years with values of F obtained at the same geographic location (interpolated from iso-intensity contours of F on World Magnetic Charts and IGRF Maps) for earlier years, suggested that over the last 75 years at this location, F has dropped from ∼49 000 nT in 1922, to ∼40 000 nT in 1996 i.e. ∼120 nT per year. Further inspection at nearby Antarctic stations reveals a drop of ∼108 nT yr −1 at Novolazarevskaya, ∼100 nT yr −1 , at Georg Forster and ∼95 nT yr −1 at Syowa; Mawson situated still further away shows a drop of ∼72 nT yr −1 , while Dumont d'Urville located very near the magnetic pole showed a drop of ∼50 nT yr −1 until 1994. A study of the observed F values over the past five decades at 23 observatories from the Antarctic and sub-Antarctic regions indicates that contours of yearly decrease in F follow a definite pattern, with maximum decrease lying in a belt encompassing Maitri. These observations are of importance in the light of modelling works at the Earth's Core–Mantle boundary pointing to two prominent regions of reverse magnetic flux (RMF) occurring beneath South America, South Africa and a large part of Antarctica, and which may merge sometime to cause reversal of the present geomagnetic field polarity. The importance of continuous monitoring of F at various locations in Antarctic and sub-Antarctic regions is brought out in this work. It is equally important to understand the cause behind this rapid decrease in F . Article in Journal/Newspaper Antarc* Antarctic Antarctic Science Antarctica Cambridge University Press Antarctic The Antarctic Indian Dumont d'Urville ENVELOPE(140.017,140.017,-66.667,-66.667) Dumont-d'Urville ENVELOPE(140.013,140.013,-66.667,-66.667) Maitri ENVELOPE(11.733,11.733,-70.764,-70.764) Dakshin Gangotri ENVELOPE(12.000,12.000,-70.083,-70.083) Antarctic Science 14 1 61 68 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Geology Ecology, Evolution, Behavior and Systematics Oceanography |
spellingShingle |
Geology Ecology, Evolution, Behavior and Systematics Oceanography Rajaram, Girija Arun, T. Dhar, Ajay Patil, A.G. Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
topic_facet |
Geology Ecology, Evolution, Behavior and Systematics Oceanography |
description |
The Indian Institute of Geomagnetism (IIG) in 1982, 1986, and 1996, operated a Proton Precession Magnetometer (PPM) at its Antarctic stations Dakshin Gangotri/Maitri (located at ∼70°S, ∼12°E). Comparison of the average quiet-time value of total intensity F for these years with values of F obtained at the same geographic location (interpolated from iso-intensity contours of F on World Magnetic Charts and IGRF Maps) for earlier years, suggested that over the last 75 years at this location, F has dropped from ∼49 000 nT in 1922, to ∼40 000 nT in 1996 i.e. ∼120 nT per year. Further inspection at nearby Antarctic stations reveals a drop of ∼108 nT yr −1 at Novolazarevskaya, ∼100 nT yr −1 , at Georg Forster and ∼95 nT yr −1 at Syowa; Mawson situated still further away shows a drop of ∼72 nT yr −1 , while Dumont d'Urville located very near the magnetic pole showed a drop of ∼50 nT yr −1 until 1994. A study of the observed F values over the past five decades at 23 observatories from the Antarctic and sub-Antarctic regions indicates that contours of yearly decrease in F follow a definite pattern, with maximum decrease lying in a belt encompassing Maitri. These observations are of importance in the light of modelling works at the Earth's Core–Mantle boundary pointing to two prominent regions of reverse magnetic flux (RMF) occurring beneath South America, South Africa and a large part of Antarctica, and which may merge sometime to cause reversal of the present geomagnetic field polarity. The importance of continuous monitoring of F at various locations in Antarctic and sub-Antarctic regions is brought out in this work. It is equally important to understand the cause behind this rapid decrease in F . |
format |
Article in Journal/Newspaper |
author |
Rajaram, Girija Arun, T. Dhar, Ajay Patil, A.G. |
author_facet |
Rajaram, Girija Arun, T. Dhar, Ajay Patil, A.G. |
author_sort |
Rajaram, Girija |
title |
Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
title_short |
Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
title_full |
Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
title_fullStr |
Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
title_full_unstemmed |
Rapid decrease in total magnetic field F at Antarctic stations - its relationship to core–mantle features |
title_sort |
rapid decrease in total magnetic field f at antarctic stations - its relationship to core–mantle features |
publisher |
Cambridge University Press (CUP) |
publishDate |
2002 |
url |
http://dx.doi.org/10.1017/s0954102002000585 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102002000585 |
long_lat |
ENVELOPE(140.017,140.017,-66.667,-66.667) ENVELOPE(140.013,140.013,-66.667,-66.667) ENVELOPE(11.733,11.733,-70.764,-70.764) ENVELOPE(12.000,12.000,-70.083,-70.083) |
geographic |
Antarctic The Antarctic Indian Dumont d'Urville Dumont-d'Urville Maitri Dakshin Gangotri |
geographic_facet |
Antarctic The Antarctic Indian Dumont d'Urville Dumont-d'Urville Maitri Dakshin Gangotri |
genre |
Antarc* Antarctic Antarctic Science Antarctica |
genre_facet |
Antarc* Antarctic Antarctic Science Antarctica |
op_source |
Antarctic Science volume 14, issue 1, page 61-68 ISSN 0954-1020 1365-2079 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0954102002000585 |
container_title |
Antarctic Science |
container_volume |
14 |
container_issue |
1 |
container_start_page |
61 |
op_container_end_page |
68 |
_version_ |
1795674658110963712 |